Pneumatic adjustable sanding device

ABSTRACT

An attachment for an oscillatory sanding or abrading device has a pair of flexible support members for supporting the sanding or abrading material. The initial radius of curvature of the flexible support member may be adjusted by a pneumatic adjustment mechanism. An opposing pair of generally cylindrical bladders are disposed proximate end portions of the flexible support member, the bladders being releasably attached between the underside of the abrading device and the support member. Adjustment of the initial radius of curvature of the flexible support is accomplished by selectively inflating one or both of the bladders. The radius of curvature of the flexible support member during the sanding process is then a function of the applied pressure or inflation of the bladders. The device allows for virtually infinitely varying adjustments of the curvature of the flexible sheet and the attached abrading sheet.

BACKGROUND OF THE INVENTION

The present invention relates to sanding and abrading devices. More particularly, it relates to an improved attachment for an automatic pneumatically powered sanding and abrading device which allows for adjustably sanding and abrading contoured surfaces.

STATEMENT OF THE PRIOR ART

Various types of sanders and abrading devices have been devised which allow for sanding and abrading contoured surfaces. These types of device are especially useful in the automotive body repair industry, as recent card designs have featured highly contoured, aerodynamic body designs. The majority of these devices are either manual devices or are designed to work with specialized actuators.

U.S. Pat. No. 5,700,187 issued to Balbi discloses a tool for sanding contoured surfaces having means for adjustably controlling the shape of the base to which the sanding material is applied. The adjustment means is relatively rigid and has a fairly complex mechanism, including a pair of screw adjusted journals which may be selectively raised, lowered, or spaced to adjust the curvature of the supporting base. The present invention, by contrast, recognizes that it is virtually impossible to exactly match the contour of any shaped surface. To that end, the present invention uses a variably adjustable pneumatic system to adjust the flexible supporting base. The pneumatic system can be selectively applied to approximate the shape of the surface to be sanded or abraded. An inflatable bladder allows the supporting base to conform to the shape of the contoured surface.

U.S. Pat. No. 5,387,251 issued to Rouse discloses another sanding device. The device is an endless belt sanding device which has a triangular frame to which sanding belts may be releasably attached. By contrast, the present invention contemplates a sanding device having a pneumatically suspended support block to which individual sanding sheets may be releasably attached.

U.S. Pat. No. 4,823,515 issued to Blome discloses an adjustable sanding device having a flexible membrane serving as a support surface for an abrasive medium. Opposing edges of the membrane are supported by spaced plates which are selectively positioned to adjust the curvature of the membrane. The present invention contemplates a support for an abrasive medium which has both a flexible membrane and a pneumatic adjustment means allowing the membrane to more fully conform to the contours of the object being sanded or abraded.

None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.

SUMMARY OF THE INVENTION

The present invention overcomes the disadvantages of the prior art by providing an attachment for an oscillatory sanding or abrading device which has an elongated flexible support member for supporting the sanding or abrading material. The initial radius of curvature of the flexible support member may be adjusted by a pneumatic adjustment mechanism. An opposing pair of generally cylindrical bladders are disposed proximate end portions of the flexible support member, the bladders being releasably attached between the underside of the abrading device and the support member. Adjustment of the initial radius of curvature of the flexible support is accomplished by selectively inflating one or both of the bladders. The radius of curvature of the flexible support member during the sanding process is then a function of the applied pressure and the inflation of the bladders. The device allows for virtually infinitely varying adjustments of the curvature of the flexible sheet and the attached abrading sheet.

Accordingly, it is a principal object of the invention to provide a new and improved attachment for sanding and abrading devices which allows for sanding and abrading contoured surfaces.

It is an object of the invention to provide a new and improved attachment for sanding and abrading devices which has a layered flexible support member for supporting the sanding or abrading material.

It is an object of the invention to provide a new and improved attachment for sanding and abrading devices which has a spring loaded support mechanism for adjusting for the contour of the surface to be sanded.

It is an object of the invention to provide a new and improved attachment for sanding and abrading devices having interchangeable springs of varying heights for adjusting the radius of curvature of the sanding material.

It is an object of the invention to provide a new and improved attachment for sanding and abrading devices having springs of varying spring constants for adjusting the flexibility of the support mechanism for the sanding and abrading material.

It is an object of the invention to provide a new and improved attachment for sanding and abrading devices having a plurality of discrete adjustments each of which allow for sanding a range of contoured surfaces.

Finally, it is a general object of the invention to provide improved elements and arrangements thereof in an apparatus for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes.

These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Various other objects, features, and attendant advantages of the present invention will become more fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views, and wherein:

FIG. 1 shows a side view, partly in section, of an automatic sanding and abrading tool with the adjustable curvature sanding attachment of the invention.

FIG. 2 shows a side view of the automatic sanding and abrading tool of FIG. 1, partly in section, detailing the connection of the apparatus to a source of pneumatic pressure.

FIG. 3A shows a perspective view, partly in section, of the abrading material and flexible support member positioned in coplanar relation to the sanding bed.

FIG. 3B shows a perspective view, partly in section, of the abrading material and flexible support member positioned in curved relation to the sanding bed.

FIGS. 4A-4C show graphical representations of several different positions of the attachment illustrating the changes in the radius of curvature of the sanding material.

DETAILED DESCRIPTION

Referring now to FIGS. 1-4C, a sanding and abrading machine attachment integrated with a standard sanding and abrading machine is shown. The attachment, generally indicated by the numeral 10, is adapted for use with a handheld pneumatic or other powered sander 12 having a flat bed 14 which is moved in a longitudinal or orbital path at a relatively high speed. These sanders 12 typically have only a single flat bed 14 with means such as clamps etc. for selectively releasing/securing strips of sanding or abrading material to be applied to a workpiece. Sanding or abrading contoured surfaces is typically done with some difficulty even by professionals, the results obtained thereby are not always satisfactory, and even in the event they are, much time is consumed in the process. To that end, the attachment 10 of the present invention is provided to facilitate sanding of contoured surfaces with superior results while minimizing the time spent by the worker.

The attachment 10 includes a lower portion 15 and an upper portion 16, the upper portion 16 comprising a pneumatic switching arrangement for selectively applying pneumatic pressure for causing a predetermined amount of curvature of the sanding and abrading surface of the lower portion 15. The lower portion of the attachment 10 contains the sanding or abrading material 24 which may be attached using an adhesive. Preferably, the sanding material 24 has an adhesive backing to allow for attachment to a support layer 27 without the use of clamps, which may cause the material to bulge or buckle as the curvature is adjusted. The support layer 27 for the sanding material 24 may be made of a relatively hard but flexible plastic material that can be easily curved into a desired shape by an expandable bellows arrangement as will be explained in more detail later. At least one metal plate 29 is attached directly to the abrading material bed 31 which is typically made of metal, and is held in place there, along with flexible support 27 by four approximately centrally positioned bolts 33 or other suitable attachment means, the bolts 33 extending into and through support later 27, plate 29, and anchored into the bed 14. The bolts 33 may be secured by nuts 35 that are accessible from the top surface of the bed 14. A pair of expandable bellows 30, 32 are securely attached to opposing end portions of the support layer 27 as by an adhesive or other secure means. The bellows 30,32 are selectively connected to a source of air pressure, and preferably, in accordance with one aspect of the invention, the same source of air pressure used to supply motive power to the flat bed 14 of the sander 12. Expansion and contraction of the bellows 30, 32 causes a corresponding change in curvature of the support layer 27. As each of the bellows 30, 32 may be separately and independently expanded or contracted, a wide range of curvatures of the support 27 may be obtained. The bellows 30, 32 are preferably made from a flexible but sturdy material such as polypropylene or other plastics, but may also be made of rubber or other suitable materials.

The adjustment of the curvature is brought about by selective application of pneumatic pressure from a source of pressurized air 37. The source of pressurized air 37 is preferably the same as that used to supply motive power for continuous oscillation of the bed. To that end, the upper portion 16 of the attachment includes a plurality of air conduits or hoses 38, 39, 40 and associated air valves 42, 44, each of the valves having manual switches 46, 48 functionally attached thereto. Input pressure is supplied via input hose 50 to a conduit 52 contained within a housing 52 securely attached to the base of the sanding apparatus 12. A hose 53 fluidly coupled to the source of pressurized air 37 supplies pneumatic pressure to regulator 60. An additional hose (not shown) is applied to the sander 12 to provide the pneumatic pressure needed for oscillating the sander bed 14. The output of the conduit 52 is fluidly coupled to branched hose 39, the hose 39 having its opposing branched ends connected to the input side of the valves 42, 44. Hoses 38, 40 have their outputs connected to respective ones of the bellows 30, 32. Switch 46 in the upright position (FIG. 2) allows pressurized air to flow into bellows 30, whereas switch 48 in the upright position allows pressurized air to flow into bellows 32. Once the desired amount of inflation of the bellows 30, 32 is achieved, both switches may be placed in the angled position as shown in FIG. 3, thereby allowing pressurized air to be received by the sander 12 and applied solely to provide motive power for bed 14.

A key aspect of the invention is the use of a pressure regulator 60 to controllably inflate the bellows 30, 32. As most pneumatic sanders are supplied with air pressure in the range of 120 psi, the pressure must be controllably stepped down in order to limit the amount of pressure supplied to the bellows 30, 32, which need no more than 5 to 7 psi to function properly.

Accordingly, pressure regulator 60 is positioned on the body of the sander 12 and secured thereto as by e.g. screws, to the housing 62. The output side of regulator 60 is fluidly coupled to conduit 50 to receive pressure from the primary pressure source. The pressure regulator 60, which may be any commercially available unit sized for convenient placement on the sander 12 supplies air pressure in the range of between 2 to 7 psi to valves 42, 44 via conduits 38, 40. Valves 42, 44 are supplied with a bleed orifice 64 and internal pressure regulators 66 as is well known, so that when the pressure within the bellows 30, 32 exceeds 5 to 7 psi, the excess pressure is released via orifices 64 creating an audible hissing sound. The hissing sound alerts the user that the bellows 30, 32 pressure has been exceeded, allowing him an opportunity to visually inspect the apparatus 10 to verify that the set curvature has been maintained. In the event that the set curvature has been lost due to excessive downward pressure applied by the user during the sanding process, the user may manipulate switches 46, 48 as described above to return support layer 27 to the desired curvature.

In operation, the user will selectively apply air to each of the bellows 30, 32, by selectively operating switches 46, 48 until a desired curvature of support layer 27 is attained. Specifically, switch 46 is positioned in the open position until bellows 30 has expanded to the desired extent and then switch 46 is repositioned to the closed position. The same procedure is used with respect to switch 48 to inflate bellows 32. Once the appropriate curvature is attained the sander 12 may then be used in the usual manner, with the inherent flexibility of the bladders 30, 32 allowing for additional conformance to the shape of the workpiece. FIGS. 4A-4C show 3 discrete positions which may be attained by selective manipulation of the bladders 30, 32, but as previously mentioned, the curvature of support layer 27 and abrading material 24 is infinitely adjustable to the limit of inflation of one or both bladders 30, 32, Unlike prior art adjustable sanders which use rigid mechanisms set to a predetermined curvature, the present invention contemplates a structure which allow first for approximation of the contour to be sanded, then the application of pressure can be used to more accurately approximate the contour of the surface to be sanded.

From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.

It is to be understood that the present invention is not limited to the sole embodiment described above, but encompasses any and all embodiments within the scope of the following claims: 

1. An attachment for a pneumatic sanding apparatus connected to a source of air pressure, said apparatus having a bed to which a sanding or abrading material may be attached, said attachment comprising: an expandable bellows arrangement having at least two bellows fluidly coupled to said source of air pressure, upper ends of said at least two bellows securely affixed to said bed; a flexible support layer having an interior surface secured to lower ends of said bellows and an exterior surface, the exterior surface of said support layer having said abrading material secured thereto; whereby curvature of said support layer may be adjusted by selective expansion and contraction of said bellows.
 2. The attachment of claim 1 wherein said at least two bellows are positioned at opposing ends of said bed.
 3. The attachment of claim 1 including switches for selectively and independently applying air pressure to said at least two bellows.
 4. The attachment of claim 1 wherein said source of air pressure is selectively coupled to said bellows by a network of conduits and valves.
 5. The attachment of claim 4 wherein each of said bellows is selectively coupled to said source of air pressure by a manually operated valve. 